Technical field
[0001] The invention relates generally to digital wireless communication through a barrier
made of a conductive material. More specifically, the invention relates to a method
and system for performing such communication, enabling communication with devices
placed inside a sealed container, preferably made of metal, using a slowly varying
magnetic field for this communication.
Background
[0002] The rapid development of the Internet Of Things technology poses new challenges in
the area of mobile communication. Most existing technologies use electromagnetic waves
(RF communication) to transmit data by air. This method of communication is efficient
in terms of energy consumption, range and speed of communication. The RF communication
is not, however, transferred through metal barriers. As a result, it is impossible
to transmit the RF signal from inside of a closed metal housing. The problem is commonly
known as the Faraday cage effect. In such cases, the radio communication cannot be
implemented and other communication methods must be used.
[0003] US20100110837A1 discloses a method for communication by means of an acoustic (mechanical) wave. This
type of communication can penetrate metal obstacles. In addition, the sound signal
can travel over long distances in a metal conductor. This solution gives good results,
but cannot be used in noisy environments, thus being useless in many applications.
[0004] EP1592142A1 discloses a method for communication through a metal barrier based on magnetic phenomena.
The use of an electromagnetic induction method brought a breakthrough in the new technology.
The solution proposed in the aforementioned document allows for communication through
a metal barrier and is completely resistant to external acoustic noise. The solution
has been developed with communication through thick metal walls in mind. Since the
receiving unit is based on an induction coil, the communication requires to use a
carrier frequency for data transmission. The solution generates large energy losses
due to eddy currents. A transmitter located inside thick metal walls would be required
to emit a large amount of energy to reach the detection sensitivity level of the receiver
component. The eddy currents can be reduced by decreasing the transmission frequency,
but this approach requires the use of large induction components.
[0005] US 8364079B2 discloses a communication method wherein the receiver can also be based on a Hall
sensor instead of an induction coil. This approach allows for communication without
using a carrier frequency, in which the signal is not so strongly attenuated by eddy
currents. The solution with a Hall sensor, which is characterized by high power consumption
and low sensitivity, does not, however, allow for miniaturization.
Summary of the invention
[0006] One of the objectives of the present invention is to propose a new method for wireless
communication through metal barriers that is free from the drawbacks of the known
solutions.
[0007] Another objective of the invention is to develop a system for digital wireless communication
system that allows for data transmission from a measuring sensor inside a cylinder
with a liquid medium, especially LPG fuel, where the measuring and communication component
must be comprised inside a brass valve closing the cylinder.
[0008] According to the first invention, there is provided a method for digital wireless
communication through a barrier 6 made of a conductive material, preferably metal,
consisting in transmission of encoded digital information using a transmitter 1, by
generation of a static magnetic field with a stepwise variable spatial orientation
of the magnetic induction vector on the first side of the barrier 6, then reading
the resulting spatial orientation of the magnetic induction vector on the second side
of the barrier 6 using at least one spatial orientation sensor of the magnetic induction
vector located in the receiver 3, and subsequently decoding the digital information
from the stepwise variable spatial orientation of the magnetic induction vector by
using a reading system 4 connected to the receiver 3, the method comprising the following
steps:
- a. generation of a static magnetic field with the first spatial orientation of the
magnetic induction vector by the first induction coil by exciting it with a current
of the first constant intensity value on the first side of the barrier 6;
- b. reading, with the receiver 3, the first resulting spatial orientation of the magnetic
induction vector of the static magnetic field produced by at least one induction coil,
which the first resulting spatial orientation of the magnetic induction vector of
the static magnetic field is additionally distorted by the barrier 6 as well as the
Earth's magnetic field and magnetic objects in the vicinity of the communication path
on the second side of the barrier 6;
- c. assigning the first digital value in the reading system 4 connected to the receiver
to the first resulting spatial orientation of the magnetic induction vector of the
static magnetic field;
- d. generation of a static magnetic field with the second resulting spatial orientation
of the magnetic induction vector of the static magnetic field by changing the static
magnetic field produced by the induction coil by changing the first value or polarity
of the excitation current of the first coil;
- e. reading, with the receiver 3, the second resulting spatial orientation of the magnetic
induction vector of the static magnetic field produced by at least one induction coil,
which the second resulting spatial orientation of the magnetic induction vector of
the static magnetic field is additionally distorted by the barrier 6 as well as the
Earth's magnetic field and magnetic objects in the vicinity of the communication path
on the second side of the barrier 6;
- f. assigning the second digital value in the reading system 4 connected to the receiver
3 to the second resulting spatial orientation of the magnetic induction vector of
the static magnetic field;
- g. encoding the digital information as a sequence of combinations of the first or
the second resulting spatial orientation of the magnetic induction vector of the static
magnetic field by the transmitter;
- h. reading the combination of the first or the second resulting spatial orientation
of the induction vector of the static magnetic field by the receiver 3 and decoding
the digital information by the reading system 4 connected to the receiver 3.
[0009] Preferably, the resulting spatial orientation of the magnetic induction vector of
the static magnetic field is generated using at least two axially non-parallel oriented
coils by independent current excitation thereof.
[0010] Preferably, the digital information is encoded with more than two resulting spatial
orientations of the magnetic induction vector of the static magnetic field.
[0011] Preferably, the spatial orientation of the magnetic induction vector of the static
magnetic field is measured in at least two geometric dimensions.
[0012] Preferably, the encoded digital information is assigned to a particular resulting
spatial orientation of the magnetic induction vector of the static magnetic field.
[0013] Preferably, the encoded digital information is assigned to a particular sequence
of at least two different resulting spatial orientations of the magnetic induction
vector of the static magnetic field.
[0014] Preferably, the reading of the spatial orientation of the magnetic induction vector
of the static magnetic field is performed with the use of highly precise MEMS, Hall
or magnetostrictive type sensors of spatial orientation of the static magnetic field.
[0015] According to the second invention, there is provided a system for performing digital
wireless communication through a barrier 6 made of a conductive material, preferably
metal, comprising a transmitter 1, a digital information encoder in the form of a
static magnetic field generator with a stepwise variable spatial orientation of the
magnetic induction vector on the first side of the barrier 6, a receiver 3 of the
spatial orientation of the magnetic induction vector on the second side of the barrier
6, a reading system 4, and a digital information decoder, wherein the static magnetic
field generator with a stepwise variable spatial orientation of the magnetic induction
vector is composed of at least one coil excited with a current of stepwise variable
intensity and polarity, and the receiver 3 comprises spatial orientation sensors of
the static magnetic field, preferably of the MEMS type.
[0016] Preferably, the receiver 3 reads the spatial orientation of the magnetic induction
vector of the static magnetic field in at least two geometric dimensions.
[0017] Preferably, the static magnetic field generator with a stepwise variable spatial
orientation of the magnetic induction vector is composed of at least two separately
excited induction coils oriented axially non-parallel to each other.
[0018] According to a third invention, there is provided a system for monitoring the level
of fluid content in a metal air-tight container, the system comprising an air-tight
container, a valve or a sealed lid, a transmitter 1 inside the cylinder, and a receiver
3 placed outside the cylinder temporarily or permanently, wherein the transmitter
1 and the receiver 3 are constructed in the form of a system according to the second
invention.
Advantageous effects of the invention
[0019] The use of the method and system according to the invention allows for effective
communication from within the metal container. Compared to prior art solutions, significant
miniaturization of the solution is possible by using a very small communication coil.
At the same time, the technology allows for a much lower energy expenditure for transmission
of information through the barrier 6. The solution can also be used for communication
through metals with a very high electrical conductivity coefficient, such as copper,
brass, aluminium.
Other advantageous effects:
[0020]
- The invention can be operated on both types of metal barriers, i.e., on those with
high magnetic permeability (e.g. steel), as well as on materials with low magnetic
permeability but very good electrical conductivity (e.g. copper, brass).
- The invention requires considerably less energy than any other reported method for
communication through the barrier 6, allowing the solution to be greatly minimized.
- The invention allows any modulation technique to be used as no carrier frequency is
required.
- Due to the low communication speed and slowly varying magnetic field, the communication
is not weakened by the barrier 6 and the parasitic effect of eddy currents arising
in the barrier.
- With the use of a high accuracy MEMS sensor, the invention can provide considerable
communication distances.
- The invention is resistant to any changes in magnetic permeability caused by variations
in the ambient temperature or chemical composition of the barrier 6.
Brief description of the Figures
[0021] Embodiments of the present inventions are shown in the drawing, where:
Fig. 1 - shows a communication scheme with all system components.
Fig. 2 - shows a solution with an E-shaped magnetic core transmitter.
Fig. 3 - shows a more complex embodiment of two-way communication.
Detailed description of preferred embodiments of the inventions
[0022] A method for digital wireless communication through a barrier 6 made of a conductive
material, according to the first invention, is schematically shown in Fig. 1.
[0023] According to a preferred embodiment, the method consists in wireless communication
through a metal barrier 6, e.g. through a wall of an LPG storage cylinder or a valve
wall. A method for digital wireless communication through a barrier 6 made of metal
(carbon fiber or other conductive material), according to the preferred embodiment,
consists in transmitting the encoded digital information using a transmitter 1. The
transmitter 1, having an induction coil and a circuit for controlling it, generates
a static magnetic field with a stepwise variable spatial orientation of the magnetic
induction vector (one piece of information corresponds to one orientation). The transmitter
1 is located on the first side of the barrier 6, typically inside the cylinder. On
the second side of the barrier 6 there is a receiver 3 which reads the resulting (distorted
by the barrier 6 and the surroundings) spatial orientation of the magnetic induction
vector by means of at least one spatial orientation sensor of the magnetic induction
vector. Then, the digital information is decoded from the stepwise variable spatial
orientation of the magnetic induction vector by means of a reading system 4 connected
to the receiver 3. The method shown in this embodiment comprises the following steps:
- a. generation of a static magnetic field with the first spatial orientation of the
magnetic induction vector by the first induction coil by exciting it with a current
of the first constant intensity value on the first side of the barrier 6;
- b. reading, with the receiver 3, the first resulting spatial orientation of the magnetic
induction vector of the static magnetic field produced by at least one induction coil,
which the first resulting spatial orientation of the magnetic induction vector of
the static magnetic field is additionally distorted by the barrier 6 as well as the
Earth's magnetic field and magnetic objects in the vicinity of the communication path
on the second side of the barrier 6;
- c. assigning the first digital value in the reading system 4 connected to the receiver
3 to the first resulting spatial orientation of the magnetic induction vector of the
static magnetic field;
- d. generation of a static magnetic field with the second resulting spatial orientation
of the magnetic induction vector of the static magnetic field by changing the static
magnetic field produced by the induction coil by changing the first value or polarity
of the excitation current of the first coil;
- e. reading, with the receiver 3, the second resulting spatial orientation of the magnetic
induction vector of the static magnetic field produced by at least one induction coil,
which the second resulting spatial orientation of the magnetic induction vector of
the static magnetic field is additionally distorted by the barrier 6 as well as the
Earth's magnetic field and magnetic objects in the vicinity of the communication path
on the second side of the barrier 6;
- f. assigning the second digital value in the reading system 4 connected to the receiver
3 to the second resulting spatial orientation of the magnetic induction vector of
the static magnetic field;
- g. encoding the digital information as a sequence of combinations of the first or
the second resulting spatial orientation of the magnetic induction vector of the static
magnetic field by the transmitter 1;
- h. reading the combination of the first or the second resulting spatial orientation
of the induction vector of the static magnetic field by the receiver and decoding
the digital information by the reading system 4 connected to the receiver 3.
[0024] In another preferred embodiment, the resulting spatial orientation of the magnetic
induction vector of the static magnetic field is generated using at least two axially
non-parallel oriented (e.g. perpendicularly aligned) coils by exciting them independently
by current.
[0025] In another, preferred embodiment, the digital information is encoded with more than
two resulting spatial orientations of the magnetic induction vector of the static
magnetic field.
[0026] If the system has one coil, it can be used to encode the digital information by quantizing
the length and sense (spatial orientation) of the magnetic induction vector of the
static magnetic field. An example could be to encode 5 cylinder capacity values 0;
25%; 50%; 100%; Overfilled cylinder; by assigning them successively the following
lengths of the vector B B
0 < B
1 < B
2 < B
4
wherein the vectors B
0 to B
4 point towards the first direction. The digital information marked "Overfilled cylinder"
can be encoded by assigning it to the vector B with the opposite sense to that of
the vectors B
0 to B
4 and any value greater than 0. This example shows how broad are the possibilities
of encoding information with only one coil and in one geometric dimension of the spatial
orientation of the induction vector (the length and sense only).
[0027] In another, alternatively preferred embodiment, where 2 coils with perpendicular
axes oriented in a plane parallel to the cylinder axis are used to encode the digital
information, the amount of encodable information increases. With two perpendicularly
arranged coils, it is possible to encode by using the length, sense or angle (direction)
of the magnetic induction vector. Such encoding can take place in two geometric dimensions
(direction and length) plus the sense.
[0028] It is also possible to use a third coil arranged non-parallel with respect to other
coils. By using 3 non-parallel, and preferably mutually perpendicular coils, it is
possible to encode in 3 geometric dimensions (direction and length) plus the sense.
[0029] The direction, sense, and length of a vector are referred to as the vector orientation.
[0030] The digital information is assigned to a particular resulting spatial orientation
of the magnetic induction vector of the static magnetic field. In another, alternatively
preferred embodiment, the digital information is assigned to a particular sequence
of at least two different resulting spatial orientations of the magnetic induction
vector of the static magnetic field.
[0031] The encoding of digital information is performed analogously to the encoding in binary
systems and relates to encoding of individual states of the system (individual "bits")
or whole "bit" words.
[0032] In a preferred embodiment, the reading of the spatial orientation of the magnetic
induction vector of the static magnetic field is performed using high precision static
magnetic field orientation sensors of the MEMS, Hall or magnetostrictive type.
[0033] An embodiment also includes a system for performing digital wireless communication
through a barrier 6 made of a conductive material, preferably metal (Fig. 1). The
system comprises:
- 1. A transmitter made of a static magnetic field emitting component, mostly a coil. The coil is an
inductive element placed, e.g. parallel to a metal barrier and can be used for communication
through the metal barrier 6 with low magnetic permeability. For communication through
a metal such as carbon steel with high magnetic permeability, a larger coil or an
E-shaped magnetic core can be used (Fig. 2).
- 2. A digital information encoder in the form of a static magnetic field generator with a stepwise variable spatial
orientation of the magnetic induction vector on the first side of the barrier 6. The
encoder is a component or circuit that converts information, e.g. digital information,
into modulation (change) of a physical quantity, e.g. wave amplitude, spatial orientation
of a physical quantity vector, e.g. polarity. The circuit typically includes an interface
(e.g. a transmitting antenna or wired jack) allowing for transmission of the modulated
physical quantity to the receiver circuit. A common solution is to first amplify the
signal with a power amplifier. An example is the radio wave modulation, e.g. amplitude
modulation (AM).
- 3. A receiver of the spatial orientation of a magnetic induction vector on the second side of the
barrier 6 of a conductive material capable of generating eddy currents under the action
of a variable magnetic field, for example a steel wall of a gas cylinder or a brass
valve.
- 4. A reading system, i.e. a sensor converting the spatial orientation of a magnetic induction vector into
an electrical or digital signal. Sensors of this type are used, for example, in electronic
compasses, they convert the angular position of the Earth's field lines (the magnetic
induction vector) into the position of the indicator on the screen or the numerical
value of an angle. Typically, these are highly sensitive magneto-impedance sensors,
e.g. magnetostrictive sensors, for example, fabricated in the MEMS technology. Their
advantage is a short conversion time, which allows for high data transmission speeds.
This component preferably comprises a digital information decoder.
- 5. A digital information decoder. The decoder (demodulator) is the opposite of a digital information encoder (modulator).
Its basic function is to separate the background measurement (the Earth's natural
magnetic field) from the useful signal generated on the second side of the barrier
6 and to decode the modulated physical signal (a series of different spatial orientations
of the induction vector) into a series of digital information, e.g. a bit sequence,
bit word or data bit value.
- 6. A barrier - an object located in the communication path between the transmitter 1 and the receiver
3, capable of interfering or preventing radio communication (performed by electromagnetic
waves). The barrier can be made of any electrically conductive material in which,
due to electromagnetic wave penetration, eddy currents are generated that attenuate
the electromagnetic signal. Typically they are metals and composites of conductive
fibers (carbon, metal, carbide).
[0034] The static magnetic field generator with a stepwise variable spatial orientation
of the magnetic induction vector is composed of at least one coil excited by a current
with a stepwise variable intensity and polarity, and the receiver has spatial orientation
sensors of a static magnetic field, preferably of the MEMS type. The receiver reads
the spatial orientation of the magnetic induction vector of the static magnetic field
in at least one geometric dimension (length and sense of the magnetic induction vector).
[0035] In another embodiment, the transmitter 1 is composed of at least two separately excited
induction coils oriented axially non-parallel to each other.
[0036] The embodiments described herein may form a system for monitoring the level of fluid
content in a metal, air-tight container, the system comprising:
- an air-tight container, valve or sealed lid,
- a transmitter 1 inside the cylinder and a receiver 3 placed outside the cylinder temporarily
or permanently.
[0037] A system for performing digital communication through a metal barrier 6 according
to the second invention is schematically shown in Fig. 3.
[0038] In a preferred embodiment, the transmitter is a single coil which generates magnetic
field due to the flow of electric current.
[0039] A permanent magnetic field is not absorbed by the barrier 6. In the case of non-magnetic
metals, such as copper, the field propagates freely through the material. In the case
of magnetic metals such as steel, the field lines close in front of the barrier, but
their presence is also measurable on the opposite side of the barrier 6.
[0040] The transmitting coil generates a magnetic field of a given orientation transmitting
the logic state 0. In the case of transmitting the logic state 1, the magnetic field
orientation is reversed by changing the polarity of the coil excitation current. In
this way, a bit stream (information flow) is generated.
[0041] The receiver 1 uses a highly sensitive magnetostrictive MEMS sensor. The operation
of the transmitter 1 disturbs the natural magnetic Earth's field, yielding a distorted,
resulting magnetic field that can be recognized by the receiver 2. This allows for
detection of a constant in time magnetic field.
[0042] The transmitter 1 generates a bitstream which, after separation of the background
from the signal, is directly received at the receiver 3. Due the possibility of transmitting
static states, the data is transmitted without modulation so that the energy loss
caused by eddy currents in the barrier is minimal. As a result, the energy required
for transmission of a message is much lower than in the case of transmitting a message
in a standard system.
[0043] In the proposed embodiment, an electronic compass - a very sensitive sensor made
in the MEMS technology is used as the receiver 3. The measurement of the magnetic
field is deliberately disturbed by a very low power signal generated on the opposite
side of the barrier 6.
[0044] The invention also includes a system for monitoring the level of fluid content in
a metal air-tight container comprising an air-tight container, a valve or a sealed
lid, a transmitter system 1 inside the cylinder, and a receiver system 2 placed outside
the cylinder temporarily or permanently using the transmitter and receiver system
as described above.
[0045] In one of the practical embodiments of the invention, the transmitter 1 is placed
inside a metal LPG cylinder, where a microprocessor-based electronic system measures
the level of a liquid inside the cylinder and transmits the level information to the
receiver 3 which is located outside the cylinder.
1. A method for digital wireless communication through a barrier (6) made of a conductive
material, preferably metal, consisting in:
transmission of encoded digital information using a transmitter (1), by generation
of a static magnetic field with a stepwise variable spatial orientation of the magnetic
induction vector on the first side of the barrier (6),
reading the resulting spatial orientation of the magnetic induction vector on the
second side of the barrier (6) using at least one spatial orientation sensor of the
magnetic induction vector located in a receiver (3), and decoding the digital information
from the stepwise variable spatial orientation of the magnetic induction vector using
a reading system (4) connected to the receiver (3),
characterised in that it comprises the following steps:
a. generation of a static magnetic field with the first spatial orientation of the
magnetic induction vector by the first induction coil by exciting it with a current
of the first constant intensity value on the first side of the barrier (6);
b. reading, with the receiver (3), the first resulting spatial orientation of the
magnetic induction vector of the static magnetic field produced by at least one induction
coil, which the first resulting spatial orientation of the magnetic induction vector
of the static magnetic field is additionally distorted by the barrier (6) as well
as the Earth's magnetic field, and magnetic objects in the vicinity of the communication
path on the second side of the barrier (6);
c. assigning the first digital value in the reading system (4) connected to the receiver
(3) to the first resulting spatial orientation of the magnetic induction vector of
the static magnetic field;
d. generation of a static magnetic field with the second resulting spatial orientation
of the magnetic induction vector of the static magnetic field by changing the static
magnetic field produced by at least one induction coil by changing the value or polarity
of the excitation current of at least one coil;
e. reading, with the receiver (3), the second resulting spatial orientation of the
magnetic induction vector of the static magnetic field produced by at least one induction
coil, which the second resulting spatial orientation of the magnetic induction vector
of the static magnetic field is additionally distorted by the barrier (6) as well
as the Earth's magnetic field and magnetic objects in the vicinity of the communication
path on the second side of the barrier (6);
f. assigning the second digital value in the reading system connected to the receiver
to the second resulting spatial orientation of the magnetic induction vector of the
static magnetic field;
g. encoding the digital information as a sequence of combinations of at least the
first or the second resulting spatial orientation of the magnetic induction vector
of the static magnetic field by the transmitter;
h. reading the combination of at least the first or the second resulting spatial orientation
of the induction vector of the static magnetic field by the receiver and decoding
the digital information in the reading system (4) connected to the receiver (3).
2. The method according to claim 1 characterised in that the resulting spatial orientation of the magnetic induction vector of the static
magnetic field is generated using at least two axially non-parallel oriented coils
by independent current excitation thereof.
3. The method according to claim 2 characterised in that the digital information is encoded with more than two resulting spatial orientations
of the magnetic induction vector of the static magnetic field.
4. The method according to claim 2 or 3 characterised in that the spatial orientation of the magnetic induction vector of the static magnetic field
is measured in at least two geometric dimensions.
5. The method according to any claim from 1 to 4 characterised in that the encoded digital information is assigned to a particular resulting spatial orientation
of the magnetic induction vector of the static magnetic field.
6. The method according to any claim from 1 to 5 characterised in that the encoded digital information is assigned to a particular sequence of at least
two different resulting spatial orientations of the magnetic induction vector of the
static magnetic field.
7. The method according to any claim from 1 to 6 characterised in that the reading of the spatial orientation of the magnetic induction vector of the static
magnetic field is performed with the use of highly precise MEMS, Hall or magnetostrictive
type sensors of spatial orientation of the static magnetic field.
8. A system for performing digital wireless communication through a barrier (6) made
of a conductive material, preferably metal, with the use of a method according to
any claim 1-7, comprising a transmitter (1), a digital information encoder (2) in
the form of a static magnetic field generator with a stepwise variable spatial orientation
of the magnetic induction vector on the first side of the barrier (6), a receiver
(3) of the spatial orientation of the magnetic induction vector on the second side
of the barrier (6), a reading system (4) and a digital information decoder (5), characterised in that the static magnetic field generator with a stepwise variable spatial orientation
of the magnetic induction vector is composed of at least one coil excited with a current
of stepwise variable intensity and polarity, and the receiver (3) comprises spatial
orientation sensors of a static magnetic field.
9. The system according to claim 8 characterised in that the spatial orientation sensor of a static magnetic field is of the MEMS type.
10. The system according to claim 8 or 9 characterised in that the receiver (3) is configured to read the spatial orientation of the magnetic induction
vector of the static magnetic field in at least two geometric dimensions.
11. The system according to claim 8 or 9 or 10 characterised in that the static magnetic field generator with a stepwise variable spatial orientation
of the magnetic induction vector is composed of at least two separately excited induction
coils oriented axially non-parallel to each other.
12. A system for monitoring the level of fluid content in a metal, air-tight container,
the said system comprising an air-tight container, a valve or a sealed lid, a transmitter
(1) inside the cylinder, and a receiver (3) placed outside the cylinder temporarily
or permanently, characterised in that the transmitter (1) and the receiver (3) are constructed in the form of a system
according to any of claims from 8 to 11.